Coffee-Derived Surfactants

ABSTRACT

Coffee-derived surfactants are provided by transesterification reactions of sugars and coffee oil. The coffee-derived surfactants are especially useful in the production of coffee oil emulsions for use with, or incorporation into, coffee products.

FIELD OF THE INVENTION

This invention is directed to coffee-derived surfactants. Morespecifically, this invention is directed to coffee-derived surfactantsprepared by transesterification reactions of sugars and coffee oil. Thecoffee-derived surfactants are especially useful in the production ofcoffee oil emulsions for use with, or incorporation into, coffeeproducts.

BACKGROUND OF THE INVENTION

Soluble coffee, also referred to as instant coffee, is a convenientalternative to the more traditional roast and ground coffee (R&G).Instant coffees, however, often trade the robust flavor of the R&G beanfor the convenience of quick preparation. Soluble coffee is typicallymade by extraction and thermal hydrolysis of roast and ground (R&G)coffee, followed by separation and drying of the extract. Often solublecoffees may have an imbalanced flavor and aroma due to the high degreeof processing and associated losses. The high temperatures and pressuresused in such processes often produce a lesser quality product ascompared to traditional R&G coffee.

The inferior quality of the soluble coffees has been a longstandingproblem. U.S. Pat. No. 5,576,044 (Nov. 19, 1996) provides an emulsionpreconcentrate which contains hydrolyzed coffee oil and a coffee aroma.Coffee oil is hydrolyzed using, for example, alkaline hydrolysis using aconventional saponification process for fats and oils. The hydrolyzedoils generally have melting points greater than about 30° C. Afteradding the appropriate coffee aroma, the emulsion preconcentrate isadded to soluble coffee particles (e.g., instant coffee). Once thecoffee beverage is prepared, a “[s]mall amount of oil may appear on thesurface, particularly if the hydrolyzed oil contains high levels ofglycerides or the soluble coffee product contains unhydrolyzed oil.However, the amount of oil on the surface is well within acceptableranges; for example equivalent to or less than that which would appearon the surface of roast and ground coffee.”

U.S. Pat. No. 4,044,162 (Aug. 23, 1977) provides a method of improvingthe flavor and aroma of decaffeinated coffee by contacting green coffeewith sucrose during the caffeine extraction process. The sucrose isreported to replace natural sucrose removed or destroyed during caffeineextraction.

U.S. Pat. No. 4,857,351 (Aug. 15, 1989) provides a method for treatingcoffee beans to improve flavor and aroma. One step in this processinvolves the treatment of partially roasted coffee beans with analkaline solution at a temperature of about 4 to about 177° C.; a sugarcan be added to the solution.

U.S. Pat. No. 6291,006 (Sep. 18, 2001) provides a so-called dissolutionagent that can be added to coffee and other beverages. The dissolutionagent preferably includes lecithin, propylene glycol, ethoxylated monoand diglycerides, and a sucrose fatty acid ester, combined withmaltodextrin and water to make a binder solution. The dissolution agentis added to the beverage product normally at a level of about 0.2 toabout 0.33 percent.

There remains a need to provide an improved and more efficient method ofproducing soluble coffee that retains the robust coffee flavor and aromasimilar to R&G coffee. There also remains a need to provide improvedsoluble coffee containing higher levels of coffee oils which, whenprepared, do not form visible “oil-slicks.”

SUMMARY OF THE INVENTION

This invention is directed to coffee-derived surfactants. Morespecifically, this invention is directed to coffee-derived surfactantsprepared by transesterification reactions of sugars and coffee oil. Thecoffee-derived surfactants are especially useful in coffee products,including the production of coffee oil emulsions for use with, orincorporation into, coffee products.

In especially preferred embodiments, this invention is directed tohighly effective emulsifiers produced from coffee materials tofacilitate the formulation of emulsions and foams in coffee products(e.g., instant coffee) and to increase the incorporation of coffee oilinto coffee products with reduced formation of so-called “oil slicks.”The coffee-derived emulsifiers are prepared using a transesterificationreaction to form sugar esters from coffee materials, especially coffeeoils, and sugars (e.g., sucrose). In one embodiment, coffee oil, anon-reducing sugar (e.g., sucrose), and an alkaline catalyst (e.g.,potassium carbonate) are reacted to provide a series of sugarmonoesters. Sugars having reducing groups (e.g., mannose) can also beused in the present invention so long as the reducing groups are blocked(e.g., via alkylation of the reducing groups; see Example 7) prior tothe transesterification reaction. For purposes of this invention, theterm “sugar” is intended to include both non-reducing and reducingsugars; as noted, however, reducing sugars should be pre-modified byblocking the reducing groups prior to the transesterification reaction.

It is generally preferred that the raw materials used to prepare thecoffee-derived surfactants are themselves derived from coffee materials.Thus, for example, sucrose used in the transesterification reaction canbe obtained from coffee materials (e.g., extracted from green coffee).Green coffee or other coffee material can be ashed and hydrated toprovide an alkaline residue which can be used in place of the alkalinecatalyst (e.g., potassium carbonate).

The coffee-derived surfactants of this invention allow the incorporationof higher levels of coffee oils in instant type coffees and provideimproved quality, reduced raw material costs, and reduced formation of“oil slicks” in instant type coffees.

DETAILED DESCRIPTION

The present invention provides coffee-derived surfactants by alkalinecatalyzed transesterification reactions of sugars with coffee materials.The resulting coffee-derived surfactants are especially useful in thepreparation of coffee oil emulsions which can then be used inpreparation of coffee beverages (especially soluble coffee beverages).The resulting coffee oil emulsions are less likely to form oil slicks,as compared to other means of adding coffee oils, in instant typecoffees. Incorporating more coffee oils in instant coffee products usingthe coffee-derived surfactants of this invention allows for improvedflavor and aroma which more closely mimics the desired robust coffeeflavor and aroma in R&G coffee. Moreover, since the surfactants areprepared from coffee materials, non-coffee surfactants are not added tothe coffee products.

Coffee-derived surfactants are prepared by alkaline catalyzedtransesterification reactions of sugars with coffee materials. Althoughnot wishing to be limited by theory, it is thought that thecoffee-derived surfactants produced in the present invention are largelya series of sugar monoesters formed during the transesterificationreactions.

Suitable coffee materials for use in the present invention include, forexample, roast and ground coffee, coffee oils, spent (i.e., partiallyextracted) coffee grounds or coffee oils, coffee aqueous extracts, greencoffee bean extracts, and the like as well as mixtures thereof; theextracts or other coffee materials may be concentrated if desired.Preferably, the coffee material comprises coffee oils.

The sugars used in the present invention include monosaccharides (e.g.,mannose, glucose, fructose, galactose and the like) and disaccharides(e.g., sucrose, lactose, maltose, trehalose, cellobiose, and the like)as well as mixtures thereof. Non-reducing sugars (e.g., sucrose,trehalose) can be used directly in the transesterification reaction.Sugars having reducing groups (i.e., reducing sugars such as mannose,glucose, fructose, galactose, lactose, maltose, and cellobiose) musthave their reducing groups blocked (see, e.g., Example 7) prior to beingsubjected to the transesterification reactions. Preferred sugars areobtained from coffee materials such as roast and ground coffee, spent(i.e., partially extracted) coffee grounds, coffee aqueous extracts,green coffee bean extracts, and the like as well as mixtures thereof.Sugars derived from coffee materials, since they mainly consist ofsucrose, can be used in the transesterification reaction without anyblocking pretreatment or preconditioning. Especially preferred coffeematerials from which sugars can be derived include spent coffee grounds.

Alkaline transesterification catalysts are used to form the desiredtransesterification products. Examples of such catalysts include K₂CO₃,KOH, NaOH, Na₂CO₃, KHCO3, NaHCO₃, and the like as well as mixturesthereof. Suitable catalysts also can be prepared from coffee materials.Thus, for example, coffee materials can be ashed (e.g., in a furnace atabout 700° C. or higher) to produce a mineral residue containing variousalkaline salts for use as the transesterification catalyst.

Generally, the transesterification reactions are carried out at about130 to about 170° C. (preferably about 140 to about 160° C.) for about 4to about 10 hours (preferably about 6 to about 8 hours) in a suitablesolvent (e.g., dimethyl formamide and the like). The desiredcoffee-derived surfactants can be obtained from the reaction mixture byremoving the solvent using conventional techniques (e.g., rotaryevaporation).

In other embodiments, the coffee materials can be treated prior to, orduring, the transesterification reaction to, for example, increase thelevel of free fatty acids in the coffee material. Thus, for example,coffee oil can be partially hydrolyzed at about 200 to about 300° C. forabout 1 to about 4 hours to increase the free fatty acids content.Subsequent treatment of coffee oil with alkaline transesterificationcatalysts may, in addition to catalyzing the transesterificationreactions, further increase the free fatty acid content. The free fattyacids are typically present as alkaline salts. Increasing the fatty acidcontent of coffee materials, such as by partial hydrolysis of coffeeoil, may beneficially increase the dispersability or functionality ofthe transesterification reaction products of this invention.

Advantages and embodiments of this invention are further illustrated bythe following examples but the particular materials and amounts thereofrecited therein, as well as other conditions and details, should not beconstrued to unduly limit the invention. All parts, ratios, andpercentages are by weight unless otherwise directed. All publications,including patents and published patent applications, are herebyincorporated by reference.

Example 1. An aqueous extract (4.5 liters) of green coffee beans havingabout 10 percent dissolved solids was adjusted to pH 4.5 by addition ofphosphoric acid. The extract was then passed through a column containingAmberlite XAD-1180 resin; the resulting eluate was then passed through acolumn containing polyamide PSC-6 resin. The resulting eluate was thenpassed through each of the columns a second time and then collected.This combination of columns is thought to preferentially remove acids,phenolic compounds, and proteins and proportionately increase thesucrose concentration. Water was added to complete the elution of thecoffee extract from the columns and added to the collected elute. Theeluate was freeze dried and then extracted with ethanol (6× by volume at80° C.). Rotary evaporation of the ethanol extract gave 6 g of paleyellow powder. Gas chromatography analysis of the powder followingtrimethylsilylation indicated that sucrose was the major component andwas present at a concentration of over 80 percent.

A mixture of sucrose fatty acid esters was produced by reacting theabove-described sucrose preparation (3.5 g) with spent grounds coffeeoil (6.0 g) in the presence of K₂CO₃ (1 g) catalyst in a polar solvent(25 ml dimethyl formamide) by heating for 8 hours in a 135° C. oil bath.K₂CO₃ was used to catalyze the transesterification reaction. K₂CO₃ isnot surface-active and does not become chemically part of the sucrosefatty acid ester molecules produced. The reaction yielded a solidifiedbrown mass (10.5 g) after rotary evaporation to remove dimethylformamide. The brown residue was then extracted with diethyl ether; theinsoluble portion (containing K₂CO₃) was discarded. The soluble portion,after removal of the diethyl ether by rotary evaporation, provided thesolidified sucrose ester reaction product. Analysis using gaschromatography (GC) confirmed the formation of fatty acids correspondingto those present in coffee oil esters plus a series of peaks that elutedafter sucrose. Analysis using liquid chromatography mass spectroscopy(LC-MS) identified these peaks as a series of sucrose monoesters.

The solidified reaction product containing the sucrose monoesters wascombined with an equal part of water using a Turrax homogenizer; anequal amount of coffee oil was then added and the mixture emulsifiedusing the Turrax homogenizer to produce a coffee oil emulsion. A drop ofthe resulting coffee oil emulsion placed on the surface of hot water.The drop dispersed without producing a visible surface slick. When asimilar amount of coffee oil is added to the surface of hot water, anoil slick is observed.

Example 2. Coffee oil (90 g), pressed from spent roasted coffee groundsobtained from a commercial soluble coffee process, was steam hydrolyzedby heating with water (10 g) at 250° C. for 2 hours in a sealed Parrbomb. Analysis indicated that the free fatty acid content of thepartially hydrolyzed oil increased from 2.1 percent initially to 47.0percent after treatment. The partially hydrolyzed coffee oil was used inExample 4.

Example 3. A mixture of sucrose fatty acid esters was produced byreacting sucrose (13.7 g) with spent grounds coffee oil (12.0 g) in thepresence of K₂CO₃ (4 g) catalyst by heating for 6 hours in dimethylformamide at 140° C. K₂CO₃ was used to catalyze the transesterificationreaction. K₂CO₃ is not surface-active and does not become chemicallypart of the sucrose fatty acid ester molecules produced. The reactionyielded a solidified brown mass (29.5 g). Analysis using gaschromatography (GC) confirmed the formation of fatty acids correspondingto those present in coffee oil esters plus a series of peaks that elutedafter sucrose. Analysis using liquid chromatography mass spectroscopy(LC-MS) identified these peaks as a series of sucrose monoesters. It wasestimated that about 5 percent of the sucrose was converted to sucrosemonoesters under these unoptimized reaction conditions.

The solidified reaction product was first combined with an equal part ofwater using a Turrax homogenizer; to this mixture was added an equalpart of coffee oil which was emulsified using the Turrax homogenizer. Adrop of the resulting (50/50) emulsion placed on the surface of hotwater. The drop dispersed without producing a visible surface slick.

For comparison purposes, sucrose (13.7 g) was combined with spentgrounds coffee oil (12.0 g) in a beaker at room temperatures without analkaline catalyst (e.g., K₂CO₃). The mixture was combined with an equalpart of water using a Turrax homogenizer and a drop of the resulting(50/50) unstable coarse emulsion placed on the surface of hot water. Avery apparent brown spotty oil slick resulted.

Example 4. The process of Example 3 was essentially repeated usingpartially hydrolyzed spent grounds coffee oil (prepared in Example 2) inplace of the spent grounds coffee oil. The reaction similarly produced amixture of sucrose monoesters.

Example 5. Green coffee beans (50 g) were ashed in a furnace at 800° C.for one hour to produce a mineral residue (4 g) containing alkalinepotassium salts. The ash (4 g) was contacted with spent grounds coffeeoil at 140° C. for 6 hours to produce free fatty acids as an alternativeto the use of K₂CO₃ obtained from a non-coffee source. The ash can alsobe used as an alternative to K₂CO₃ obtained from a non-coffee source tocatalyze the transesterification reaction to form the surfactantcompositions of this invention. Thus, this material could be used, forexample, to replace the K₂CO₃ catalyst of Example 1 to provide asurfactant composition prepared only from coffee-derived materials.

Example 6. Ethanol was produced from an aqueous extract of green coffeebeans by microbial fermentation using yeast from the Saccharomycesgenus. Such ethanol, which is derived from coffee materials, can be usedwith sugars containing reducing groups to “block” (e.g., alkylation ofthe reducing groups). Such ethanol, for example, could be used asdescribed in Example 7 to produce coffee-derived surfactants; ifcombined with the coffee-derived catalyst of Example 5, surfactantcompositions prepared only from coffee-derived materials could beobtained.

Example 7. A mixture of ethyl mannose fatty acid esters was produced byfirst reacting mannose (1.8 g) with ethanol (20 g) in the presence ofDowex cation-exchange resin in its W form to catalyze production ofethyl mannose (2.1 g) and thereby blocking the reducing groups. Ethylmannose (2 g) was then reacted with spent grounds coffee oil (3 g) inthe presence of K₂CO₃ (1 g) by heating for 6 hours in a 140° C. oilbath. K₂CO₃ was used to catalyze the transesterification reaction. K₂CO₃is not surface-active and does not become chemically part of the ethylmannose fatty acid esters produced. The reaction yielded a solidifiedbrown mass (6 g). Analysis using gas chromatography (GC) confirmed theformation of fatty acids corresponding to those present in coffee oilesters plus a series of peaks that eluted after mannose. Analysis usingLC-MS identified these peaks as a series of ethyl mannose monoesters. Itwas estimated that 0.5 percent of the mannose was converted to ethylmannose monoesters under these unoptimized reaction conditions. Thesolidified reaction product was combined with an equal part of waterusing a Turrax homogenizer and a drop of the resulting (50/50) emulsionplaced on the surface of hot water. The drop dispersed without producinga visible surface slick.

For comparison purposes, mannose (1.8 g) was combined with spent groundscoffee oil (3.0 g) in a beaker at room temperatures without the use ofan alkaline catalyst. The mixture was combined with an equal part ofwater using a PowerGen 700D mixer (Fisher Scientific) and a drop of theresulting (50/50) unstable coarse emulsion placed on the surface of hotwater. A very apparent brown spotty oil slick resulted.

Example 8. Roasted spent coffee grounds were contacted with water athigh temperature using a commercial thermal hydrolysis process toprepare an aqueous coffee extract having a high concentration ofmannose. The resulting extract could be used in the place of mannose inExample 7 to prepare mannose monoesters using only coffee-derivedmaterials.

Example 9. The sucrose monoester-containing reaction product (0.16 g) ofExample 3 was combined with soybean oil (8.0 g), Maxwell House InstantCoffee powder (2.0 g), and water (7.84 g) and sheared using a PowerGen700D mixer to produce a stable water-in-oil emulsion having average oildroplet size of 8 microns.

Example 10. The sucrose monoester-containing reaction product (1.6 g) ofExample 3 was combined with Maxwell House Instant Coffee powder (2.0 g),and water (230 g) in a 12 ounce cup and whipped using a PowerGen 700Dmixer at 20,000 rpm for 30 seconds to produce a foamed coffee beveragehaving the appearance of espresso.

1.-10. (canceled)
 11. A method of producing coffee-derived surfactants,said method comprising (1) reacting a coffee material and a sugar in asolvent in the presence of an alkaline transesterification catalyst fora time and at a temperature effective to prepare a coffee-derivedsurfactant-containing reaction mixture by transesterification reactions;(2) removing the solvent from the coffee-derived surfactant-containingreaction mixture to provide a coffee-derived surfactant-containing solidresidue; (3) removing the alkaline transesterification catalyst from thecoffee-derived surfactant-containing solid residue to obtain thecoffee-derived surfactants, wherein the sugar is a monosaccharide, adisaccharide, or a mixture thereof; wherein the sugar is non-reducing orreducing; and wherein, if the sugar is reducing, the sugar is treatedprior to step (1) to block reducing groups therein.
 12. The method ofclaim 11, wherein step (1) is carried out at about 130 to about 170° C.for about 4 to about 10 hours.
 13. The method of claim 12, wherein thecoffee material is selected from the group consisting of roast andground coffee, coffee oil, spent coffee ground, spent coffee oil, coffeeaqueous extract, green coffee bean extract, and mixtures thereof. 14.The method of claim 13, wherein the coffee material is coffee oil. 15.The method of claim 13, wherein the sugar is selected from the groupconsisting of mannose, glucose, fructose, galactose, sucrose, lactose,maltose, trehalose, cellobiose, and mixtures thereof.
 16. The method ofclaim 14, wherein the sugar is selected from the group consisting ofmannose, glucose, fructose, galactose, sucrose, lactose, maltose,trehalose, cellobiose, and mixtures thereof.
 17. The method of claim 13,wherein the sugar is derived from a second coffee material selected fromthe group consisting of roast and ground coffee, spent coffee grounds,coffee aqueous extract, green coffee bean extract, and mixtures thereof.18. The method of claim 14, wherein the sugar is derived from a secondcoffee material selected from the group consisting of roast and groundcoffee, spent coffee grounds, coffee aqueous extract, green coffee beanextract, and mixtures thereof.
 19. The method of claim 13, wherein thealkaline transesterification catalyst is derived from a third coffeematerial selected from the group consisting of roast and ground coffee,spent coffee grounds, coffee aqueous extract, green coffee bean extract,and mixtures thereof, wherein the third coffee material has been ashedto provide an alkaline mineral residue.
 20. The method of claim 14,wherein the alkaline transesterification catalyst is derived from athird coffee material selected from the group consisting of roast andground coffee, spent coffee grounds, coffee aqueous extract, greencoffee bean extract, and mixtures thereof, wherein the third coffeematerial has been ashed to provide an alkaline mineral residue.
 21. Asoluble coffee comprising: a coffee-derived sugar-fatty acid estercomposition; and a soluble coffee composition, wherein thecoffee-derived sugar-fatty acid ester composition includes a sugarresidue selected from the group consisting of monosaccharides,disaccharides and mixtures thereof derived from a first coffee materialtreated to increase the level of sugar and remove at least a portion ofacids, phenolic compounds and proteins and a fatty acid residue derivedfrom a second coffee material, the coffee-derived sugar-fatty acid estercomposition further including unreacted coffee material and coffeematerial by-products in addition to sugar-fatty acid esters, wherein thefirst coffee material is selected from the group consisting of roast andground coffee, spent coffee ground, coffee aqueous extract, green coffeebean extract, and mixtures thereof, and wherein the second coffeematerial is selected from the group consisting of roast and groundcoffee, coffee oil, spent coffee ground, spent coffee oil, coffeeaqueous extract, green coffee bean extract, and mixtures thereof. 22.The soluble coffee of claim 21, wherein the second coffee material iscoffee oil.
 23. The soluble coffee of claim 21, wherein the sugarresidue includes sugar selected from the group consisting of mannose,glucose, fructose, galactose, sucrose, cellobiose and mixtures thereof.24. The soluble coffee of claim 21, wherein the sugar-fatty acid esteris a surfactant that is the transesterification product of a sugarderived from the first coffee material with the second coffee materialusing an alkaline transesterification catalyst derived from a thirdcoffee material.
 25. The soluble coffee of claim 24, wherein the first,second and third coffee materials are the same.
 26. The soluble coffeeof claim 24, wherein the third coffee material is an ashed coffeematerial.
 27. The soluble coffee of claim 21, wherein the first coffeematerial is treated to contain at least 80% sugars.
 28. A coffee-derivedsurfactant comprising: a sugar-fatty acid ester composition whichincludes a transesterification product of a sugar derived from a firstcoffee material with a coffee oil using an ashed coffee material as analkaline catalyst, wherein the sugar-fatty acid ester compositionincludes a sugar residue and a fatty acid source, the sugar residueselected from the group consisting of monosaccharides, disaccharides andmixtures thereof derived from the first coffee material and the fattyacid source being the coffee oil such that the sugar-fatty acid esterdoes not include any non-coffee derived materials, wherein thesugar-fatty acid composition further includes unreacted coffee materialand coffee material by-products.
 29. The coffee-derived surfactant ofclaim 28, wherein the first coffee material is selected from the groupconsisting of roast and ground coffee, spent coffee ground, coffeeaqueous extract, green coffee bean extract, and mixtures thereof. 30.The coffee-derived surfactant of claim 28, wherein the coffee-derivedsurfactant is added to water to create a stable oil-in-water emulsion.31. The coffee-derived surfactant of claim 30, wherein the oil-in-wateremulsion has an average droplet size of 8 microns.